In a high-frequency circuit unit of a mobile terminal such as cellular phone and smartphone, a transmitter circuit and a receiver circuit are selectively connected to a common antenna through a switch circuit for high-frequency signals (hereinafter referred to as a high-frequency switch circuit). Conventionally, a HEMT (High Electron Mobility Transistor) using a compound semiconductor has been used as a switch element of such a high-frequency switch circuit. However, due to the demands for price reduction and downsizing in recent years, it has been studied to use a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) formed on a silicon substrate, instead of the HEMT.
Note that a general MOSFET formed on a silicon substrate has such problems that the parasitic capacitance between the source or drain electrode and the silicon substrate is large, and that power loss of high-frequency signals is large since silicon is a semiconductor. Thus, a technique for forming the high-frequency switch circuit on an SOI (Silicon On Insulator) substrate has been proposed.
Recent mobile terminals operate in multimode and multiband, and the number of RF signals to be switched by the high-frequency switch has been increased correspondingly.
A switch control circuit for controlling the switching of the high-frequency switch operates at a low-potential logic level, while the high-frequency switch circuit requires larger voltage amplitude than that of the switch control circuit since the high-frequency switch circuit has to transmit and receive RF signals to and from an antenna. For this reason, generally, the switch control circuit has a negative potential generating circuit and a driver circuit to convert potential level by the driver circuit using the negative potential generated by the negative potential generating circuit.
However, there is a likelihood that the output potential of the negative potential generating circuit greatly rises temporarily at the time of switching, and thus a large capacitor is connected between the output terminal of the negative potential generating circuit and a ground terminal in many cases. However, as the size of this capacitor becomes larger, a time required until the output signal from the negative potential generating circuit reaches a desired potential level becomes longer. In order to shorten this time, the capability of a charge pump of a charge pump circuit in the negative potential generating circuit may be increased, but this increases power consumption of the negative potential generating circuit.